#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <arpa/inet.h>

#define MYPORT 5000

int main(int argc, char const *argv[])
{
    int sockfd;
    struct sockaddr_in their_addr;
    struct hostent *he;
    int numbytes;

    if(argc!= 3) {
        fprintf(stderr, "usage: talker hostname message\n");
        exit(1);
    }

    if((he = gethostbyname(argv[1])) == NULL) {
        herror("gethostbyname");
        exit(1);
    }

    if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    their_addr.sin_family = AF_INET; // 主机
    their_addr.sin_port = htons(MYPORT);
    their_addr.sin_addr = *((struct in_addr*)he->h_addr);
    bzero(&(their_addr.sin_zero), 8);
    if((numbytes = sendto(sockfd, argv[2], strlen(argv[2]), 0, (struct sockaddr*)&their_addr, sizeof(struct sockaddr))) == -1) {
        perror("sendto");
        exit(1);
    }
    printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));

    close(sockfd);
    return 0;
}